Google Designing 'X Phone' to Rival Apple, Samsung

By

Amir Efrati

Updated Dec. 21, 2012 7:26 p.m. ET

Engineers at Motorola Mobility are hard at work on a sophisticated handset—known internally as the "X phone"—but the Google Inc. unit is running into some obstacles in its effort to provide more potent competition for Apple Inc., said people familiar with the matter.

Seven months after being acquired by Google for $12.5 billion, Motorola is designing its marquee handset with cutting-edge features to stand apart from existing...